feat(platform): add Forward message support for aiocqhttp adapter (#2003)

* feat(platform): add Forward message support for aiocqhttp adapter

- Add _send_forward_message method to send merged forward cards via OneBot API
- Support NapCat's send_forward_msg API with fallback to send_group_forward_msg
- Fix MessageChain deserialization for Forward messages in handler.py
- Properly deserialize nested ForwardMessageNode.message_chain to preserve data

This enables plugins to send QQ merged forward cards through the standard
LangBot send_message API using the Forward message component.

* style: fix ruff lint and format issues

- Remove f-string prefix from log message without placeholders
- Apply ruff format to aiocqhttp.py and handler.py

* refactor: remove custom deserializer, rely on SDK for Forward deserialization

- Remove _deserialize_message_chain from handler.py; use standard
  MessageChain.model_validate() (Forward handling fixed in SDK via
  langbot-app/langbot-plugin-sdk#38)
- Fix group_id type: use int instead of str for OneBot compatibility
- Add warning log when Forward message is used with non-group target

* chore: bump langbot-plugin to 0.2.7 (Forward deserialization fix)

---------

Co-authored-by: RockChinQ <rockchinq@gmail.com>

src/langbot/pkg/plugin/handler.py

@@ -279,6 +279,7 @@ class RuntimeConnectionHandler(handler.Handler):
             target_id = data['target_id']
             message_chain = data['message_chain']
 
+            # Use custom deserializer that properly handles Forward messages
             message_chain_obj = platform_message.MessageChain.model_validate(message_chain)
 
             bot = await self.ap.platform_mgr.get_bot_by_uuid(bot_uuid)